Echocardiographic index of left ventricular performance for prognostication in transthyretin cardiac amyloidosis: the central role of stroke volume index

INTRODUCTION: Cardiac amyloidosis typically causes restrictive cardiomyopathy, in which the impairment of diastolic function is dominant. Echocardiography provides prognostic information through some important parameters: left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS). However, LVEF often remains preserved despite disease progression, and GLS is not routinely performed as it is limited by suboptimal image quality. The stroke volume index (SVi) has already been shown to correlate with mortality in heart failure patients; still, its prognostic role in transthyretin cardiac amyloidosis (TTR-CA) is poorly studied. PURPOSE: This prospective study aimed to evaluate the role of SVi in predicting mortality and heart failure hospitalizations in patients with cardiac amyloidosis, comparing it to other parameters of left ventricular performance. METHODS: Baseline clinical transthoracic echocardiogram and laboratory data were collected prospectively in 115 patients with diagnosed TTR-CA. The outcome was the occurrence of the composite of heart failure hospitalization and death and its association with SVi, LVEF, GLS and MCF was tested by Cox proportional hazard modelling. RESULTS: Over a mean follow-up of 16.1 months (interquartile range 7.4-24.9 months), 29 patients died, and 19 were hospitalized for heart failure. SVi was associated with the composite outcome of death and heart failure hospitalization [hazard ratio 0.96; 95% confidence interval (CI) 0.93-0.99] and remained an independent predictor of outcome after adjustment for NAC stage, mitral regurgitation degree, age and the use of disease-modifying treatment. The best cut-off of SVi to predict outcome was 35 ml/m2 (hazard ratio 2.30; 95% CI 1.03-5.17). CONCLUSION: SVi is superior to LVEF, MCF, and GLS for prognostication in patients with TTR amyloidosis.